Its unclear when the C4 was first introduced, but the date 1991 is wrong. The mask is also made of bromo-butyl, only silicone is used for a few parts like the oral nasal cup and drinking tube. The part where you mentioned the c2 being the same as the American one is right, because we were the original designers of the c2 filter. The Forsheda filter was copied from Airboss which also produces the c7 canister. It should also be noted that early c4's that were produced in black and some green ones were made by DREO, and the production switched to Airboss when problems arose with lower quality assembly. The PC-4 was intended for law enforcement and security and the later black variant (not to be confused with the early C4) is for civilians. Little is known about the tan variant but it was likely for use in Afghanistan and other desert countries where us Canadians were deployed, however it never made it into mass production. Awesome video, looking forward to the next one.
